The invention relates to electronic semiconductor devices, and, more particularly, to gate structures and fabrication methods for integrated circuits.
The trend in semiconductor integrated circuits to higher device densities by down-scaling structure sizes and operating voltages has led to silicon field effect (MOS) transistor gate dielectrics, typically made of silicon dioxide, to approach thicknesses on the order of 1-2 nm to maintain the capacitive coupling of the gate to the channel. However, such thin oxides present leakage current problems due to carrier tunneling through the oxide. Consequently, alternative gate dielectrics with greater dielectric constants to permit greater physical thicknesses have been proposed. Indeed, Ta2O5, (Ba,Sr)TiO3, and other high dielectric constant materials have been suggested, but such materials have poor interface stability with silicon.
Wilk and Wallace, Electrical Properties of Hafnium Silicate Gate Dielectrics Deposited Directly on Silicon, 74 Appl. Phys. Lett. 2854 (1999), disclose measurements on capacitors with a hafnium silicate dielectric formed by sputtering (at a pressure of 5xc3x9710xe2x88x926 Torr and substrate temperature of 500xc2x0 C.) a 5-nm thick layer of Hf6Si29O65 directly onto silicon together with a gold top electrode deposited on the silicate dielectric. Such capacitors showed low leakage current, thermal stability, an effective dielectric constant of about 11, and a breakdown field of 10 MV/cm.
However, such silicate dielectrics need better electrical properties for use in high volume production silicon integrated circuits.
Total reflection X-ray fluorescence (TXRF) is an analysis tool useful in integrated circuit manufacturing for detection of surface contaminants. For example, Liou et al, Applications of Total Reflection X-Ray Fluorescence to Analysis of VLSI Micro Contamination, 12 IEEE Trans. Semi. Manuf. 266 (1999) and Smith et al, Understanding the Correlation of TXRF and SurfaceSIMS, 1998 Intl. Conf. Ion Implantation Proc. 1063 (1998).
The present invention provides integrated circuit fabrication with total reflection x-ray fluorescence for composition control of silicate dielectrics.
This has the advantages including non-destructive control.